Wire feeders are used in various welding or cladding applications to feed wire to the welding or cladding spot. Such wire can be referred to as filler wire, additive wire or consumable wire.
Hot wire welding/cladding is a process where a metal filler wire is resistively heated, typically, to a softened/plastic/semi-liquidus state, usually by passing an electrical current through it. This reduces the amount of added heat from another high-power energy source needed for the base metal of a workpiece to which the heated wire is applied. Beneficially, heating up the wire rids it of moisture, so when it enters the welding/cladding puddle it's free of porosity, it's clean and the quality is significantly better than cold wire. The wire is typically fed in front of or behind a high-power energy source such as a laser or plasma that further melts the wire material or the wire material along with the base metal of the workpiece to produce a weld or clad. In TIG welding, the wire is fed to the TIG arc.
In arc welding processes, such as gas metal arc welding or flux-cored arc welding, an electrode wire is used to produce the weld. An arc created between the electrode and the base metal of the workpiece is used to melt a portion of the workpiece to form a molten puddle that when solidified creates a weld.
In both cases, the wire is fed into or near the puddle. This way, when a workpiece is moved relative to the welding arrangement (with either the workpiece moved or the welding equipment moved), the puddle can be maintained to create a continuous weld or cladding layer.
In hot wire welding, the start of wire feeding is sequenced very precisely to prevent arcing, or overfeeding of the wire before the process can stabilize and be in a steady state. Commonly, first the wire feed is initiated. Second, the wire contacts the workpiece. Third, heating power (e.g., electrical current applied through the wire, which has some resistance) is applied to the wire. Fourth, the wire heats to a plastic/semi-liquidus phase at the weld/clad spot, namely the weld/clad puddle. Fifth, feeding and sustained high-power energy heating of the wire occurs in the steady state.
The use of hot wire welding, such as tungsten inert gas welding, tends to be more part-related and industry-related. For example, hot wire TIG is used extensively in the transportation and power generation industries. It's big in shipbuilding, and for rebuilding turbine shafts for large power plants. Hot wire TIG also is used in cladding very large valve welds such as those for oil industry in which welders clad the inside of the valve weld with high-performance alloys.
Additionally, wire feeders can be used in additive manufacturing, sometimes referred to as 3D printing. In additive manufacturing, wire is melted to make a three-dimensional object. To that end, successive layers of melted wire are laid down under computer control. These objects can be of almost any shape or geometry, and can be produced from a 3D model or other electronic data source.